FWRI researchers use satellite telemetry to study the migratory
behavior and habitat use patterns of sea turtles.

Satellite telemetry is a powerful research tool that helps
scientists understand how highly migratory animals interact with
their environment. Sea turtle researchers use satellite telemetry
to reconstruct long-distance sea turtle migrations and to describe
the resident areas used by these animals. With telemetry,
scientists can learn how far sea turtles travel, how fast they swim
during migration, what routes they follow, and more. Researchers
are also using this technology to determine whether sea turtles use
environmental cues (such as ocean currents) as navigational aids
during migration. Data collected during these studies often
indicate long-term periods of residency in distinct foraging
habitats.

Satellite telemetry allows researchers to track the movement of
an animal by using orbiting satellites that detect signals emitted
from a transmitter attached to the animal. On the carapace (top
shell) of hard-shelled sea turtles, transmitters are attached with
epoxy or fiberglass and resin. The attachment methods are designed
to be harmless and are constantly being improved to ensure the
health and safety of the animals being tracked.

Success of this technique depends on the satellites' ability to
receive the radio signals from the transmitters. However, signals
are not transmitted when the transmitter is underwater and cannot
be received if the satellites are not within range. Each
transmitter has a sensor that detects when the unit is above water
and acts as the unit's "on/off" switch. Switching off while
underwater preserves the battery by allowing transmissions only
when the unit is above water and capable of communicating with
satellites. Typically, a sea turtle's transmitter will be above
water only when the turtle surfaces to breathe. This limitation is
one of the main factors influencing the amount and accuracy of
these positional data.

The distance between the transmitter and the satellites is
calculated based on the transmitter signals, and the location of
the transmitter on the ground is geometrically determined.
Transmitters that have GPS receivers can collect more precise
positional information than those derived from the radio
frequencies alone. Transmitters can be equipped with additional
sensors that measure depth, temperature, and light. Successful
transmissions are relayed from the satellites to receiving stations
on the ground where the data are processed and then provided daily
to researchers via the internet. Researchers typically receive
several locations each day, but this may decrease to several per
week as the transmitter battery begins to expire. Such detailed
information allows scientists to track telemetered animals daily
and obtain clues about their behavior throughout migratory
journeys.

During the summer of 2010, in collaboration with Dr. Tony Tucker
of Mote Marine Laboratory, five satellite transmitters were
deployed on adult female loggerheads that had nested on Casey Key
Beach, Sarasota County, Florida. The information they gather
supplements a larger dataset that will help describe the habitat
preferences of loggerhead sea turtles in the Gulf of Mexico and
surrounding waters. These transmitters have GPS receivers as well
as sensors that describe the sea turtles' diving behavior and
foraging habits. Satellite telemetry data from these transmitters
are presented in near-real time on
SeaTurtle.org.

Funding for current satellite telemetry research is provided by
the National Marine Fisheries Service's cooperative agreement with
the State of Florida as prescribed by Section 6 of the Endangered
Species Act of 1973 (award number: NA10NMF4720031).